An express train travel from A to B for 4 hours. A normal train travel from B to A for 10 hours. Both of them started at the same time. The average speed of the express train is greater than the average speed of the normal train 90km/h. Find the average speed of the normal train?

The speed of the normal train is 60 kilometers per hour.

Step-by-step explanation:

Let suppose that both trains move at constant speed and cover the same distance. Then, we have the following identity:

(1)

Where:

- Average speeds of the express train and the normal train, in kilometers per hour.

- Travel times of the express train and the normal train, in hours.

In addition, there is the following relationship between average speeds:

(2)

By (2) in (1), we have the following expression for the average speed of the normal train:

If we know that and , then the average speed of the normal train is:

The speed of the normal train is 60 kilometers per hour.

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this

search the worksheet up on the internet

step-by-step explanation:

it works trust me